Multiwall bag construction

ABSTRACT

A bag formed of spunbonded material has an outer surface and at least one ply of paper secured to the outer surface in order to reduce actinic degradation of the olefinic polymer material.

United States Patent [1 1 Kilgore Jan. 8, 1974 MULTIWALL BAGCONSTRUCTION [75] Inventor: William E. Kllgore, Palatka, Fla.

[73] Assignee: Hudson Pulp & Paper Corporation,

Palatka, Fla.

22 Filed: Mar. 17, 1971 211 App]. No.: 125,310

[52] U.S. Cl 229/55, 161/251, 206/DIG. 34, 229/53 [51] Int. Cl B65d33/02 [58] Field of Search 229/3.5 R, 53, 55; 206/D1G. 34; 161/150, 250,253

[56] References Cited UNITED STATES PATENTS 3,297,515 1/1967 Regenstein,Jr. et a1. 161/253 3,630,816 12/1971 Parker 161/150 3,248,041 4/1966Burke 229/55 3,331,501 7/1967 Stewart, Jr.. 229/55 3,305,160 2/1967Lehman" 229/55 3,325,082 6/1967 Naylor 229/55 Primary ExaminerWilliam T.Dixson, Jr. Assistant ExaminerStephen Marcus Attorney-Curtis, Morris &Safford [5 7] ABSTRACT A bag formed of spunbonded material has an outersurface and at least one ply of paper secured to the outer surface inorder to reduce actinic degradation of the olefinic polymer material.

15 Claims, 6 Drawing Figures MULTIWALL BAG CONSTRUCTION This inventionrelates to bag constructions and more particularly to bags formed of aspunbonded olefinic polymer material or other materials which aresubject to actinic degradation.

It has previously been proposed that bags formed of an olefinic polymermaterial, such as, for example polypropylene, be utilized in a number ofexterior applications such as for military sand bags and rip-rap bags.While such bags have proved generally satisfactory in use, the lifeexpectancy thereof is seriously reduced by actinic degradation of thepolypropylene fibers caused by exposure to the ultraviolet rays of thesun. Typically it has been found that failure of such bags occurs withinless than three months after initial exposure.

Attempts have been made to extend the life of these bags by inclusion ofinorganic and organic ultraviolet inhibitors within the material itself.Such inhibitors include carbon black, titanium dioxide and zinc oxide.While these inhibitors have achieved a stabilizing effect by convertingthe ultraviolet light into relatively harmless longer wave lengths, itis relatively expensive to include these materials in the polyolefinsheet material from which the bag is made. Further, the life expectancyof the bags is not increased sufficiently to justify the additionalexpense of combining these inhibitors with the polyolefin material.

Accordingly, it is an object of the present invention to reduce the rateof actinic degradation of bags formed of a polyolefinic material orother materials subject to this type of degradation.

It is another object of the invention to substantially increase theuseful life expectancy of polypropylene in bags.

Yet another object of the invention is to provide a web materialincluding a layer of olefinic polymer material adapted to produce a baghaving a long life expectancy and which is inexpensive in constructionand light in weight.

In accordance with an aspect of this invention, a bag construction isprovided in which an inner bag formed of a sheet of olefinic polymermaterial is provided with at least one ply of paper secured to its outersurface to provide a barrier to utlraviolet light whereby to reduceactinic degradation of the olefinic polymer material.

In the preferred embodiment of the invention the material of which theinner ply is formed is a sheet of spunbonded polypropylene having anouter covering of kraft paper secured thereto by suitable adhesive.

The paper sheet may be formed from a plurality of plies of paperlaminated in superimposed relation on the surface of the spunbondedpolypropylene sheet to increase the size of the barrier and furtherlimit light penetration to the olefinic material. The polypropylenesheet may be provided with a layer or ply of paper on both sides thereofto not only prevent or limit light penetration to the sheet but also toprevent contamination of the articles within the bag with polypropylenefibers.

The above and other objects, features and advantages of this inventionwill be apparent in the following description of illustrativeembodiments of the invention which are to be read in connection with theaccompanying drawings wherein:

FIG. 1 is a perspective view of a bag constructed in accordance with oneembodiment of the present invennon;

FIG. 2 is a sectional view of a composite web utilized in accordancewith the present invention;

FIG. 3 is a sectional view of another embodiment of the composite webconstructed in accordance with the present invention;

FIGS. 4 and 5 are sectional views of still other embodiments of the webstructure; and

FIG. 6 is a sectional view of another embodiment of the web structure inaccordance with the present invention, including a waterproofing liner.

Referring now to the drawings in detail, and initially to FIG. 1thereof, it will be seen that a bag 10 of the type in which the presentinvention may be employed generally comprises a main bag portion 12formed of an olefinic polymer material and an outer paper covering 14therefor. Main bag portion 12 is particularly adapted to be used forsand bags and for rip-rap bags wherein the bags are filled with sand orsand-cement mixture and placed at bridge bulkheads, sea walls, landfills and the like. The bags formed of olefinic polymer materials forsuch uses are highly desirable in that the bag construction isrelatively inexpensive and the material has sufficient strength tocontain the sand while being able to absorb the normal impacts andshocks incurred during use. However, one disadvantage of such bags isthat the olefinic polymer material, which is preferably polypropylene inthe form of a spunbonded sheet, is susceptible to actinic degradationwhen exposed to the ultraviolet rays of the sun, which rays activatedegradation and oxidation reactions causing brittlement anddeterioration of the bags.

The provision of outer paper covering 14 for polypropylene bag 12, inaccordance with the present invention, produces a substantial increasein the life expectancy of the polypropylene bag, in addition to numerousother advantages. Outer covering 14 in one embodiment of the inventionconsists of an outer paper ply which receives and thereby covers thefree or laminated polypropylene ply to provide a barrier to thepenetration of ultraviolet rays produced by the sun.

As seen in FIG. 1, bag 10 is provided with a closure strip 16 which maybe sewn to the edges of the bag adjacent the top opening to close thetop of the bag when the latter is filled. However, it is contemplatedthat other conventional attaching mechanisms, such as for examplestrings or other known bag closure mechanisms may be utilized to closethe top of the bag.

As mentioned, outer covering 14 is, in one embodiment, a paper bag inwhich the inner polypropylene bag is inserted. However, it is alsocontemplated that this covering may be in the form of a bag or sheets ofpaper which are secured to the polypropylene bag 12 in any convenientmanner. For example, covering 14 may be secured to bag 12 by tacking orstitching.

In this manner a web construction is produced which, as seen in FIG. 2,includes a first layer 12 of polypropylene or other olefinic materialutilized to form main bag 12 and an outer layer 20 of paper. It is notedthat the paper utilized in conjunction with the present invention may beany suitable paper which significantly reduces penetration ofultraviolet light to the polypropylene sheet. However, in the preferredconstruction the paper utilized is a kraft or crepe paper which may beeither natural or extensible.

A laminated web construction may also be utilized to form bag 10 andmaintain the advantages of polypropylene bag construction for sandbagand rip-rap bag usage while simultaneously providing an outer coveringwhich resists the penetration of ultraviolet rays. Referring to FIG. 3of the drawings, it is seen that a layer 22 of polypropylene material isprovided which has an outer surface 24 to which a ply 26 of paper issecured by means of a layer 28 of adhesive material. The adhesivematerial may be any of those adhesives known to those skilled in the artfor laminating paper materials together. Such adhesives may for example,constitute asphalt, hot melt adhesive, latex, acetate, polymer waxblend, or solution adhesive. The laminated web constructed in thismanner is formed into a composite sheet which is then utilized to formbag 10.

It has been found that bags constructed in accordance with the presentinvention, that is, bags having an inner bag formed of polypropylene andan outer covering of paper have an increased life expectancy of fromthree to five months above bags formed only of polypropylene. This istrue whether the outer covering merely constitutes an outer bag as inthe embodiment disclosed in FIGS. 1 and 2 or whether the outer ply ofpaper is laminated or partially laminated to the outer surface of thepolypropylene sheet.

It has also been found that additional increases in life expectancy areobtained by utilizing additional plies of paper on the outer surface ofthe polypropylene in order to further reduce the amount of ultravioletrays reaching the polypropylene sheet. Referring to FIG. 4 of thedrawings another embodiment of the invention is shown wherein aplurality of layers or plies 30 of paper are laminated to the outersurface 24 of polypropylene sheet 22. These plies may be laminated tothe polypropylene sheet in any desirable configuration, as for examplewith a crosshatch pattern.

By laminating the paper plies to the polypropylene sheet additionaladvantages are obtained in that the laminant or adhesive holds the paperto the polypropylene sheet. This is particularly important since thepolypropylene sheet has the ability to stretch up to 50 percent of itslength whereas paper stretches only 1 percent to 8 percent of itslength, and thus, when a bag is dropped, it may occur that the paperwill split or tear while the polypropylene sheet will remain integral.The laminant in this case holds the broken paper ply in its placewhereby the paper continues to serve as an ultraviolet barrier afterdropping or breaking. In addition, the laminant prolongs the life of thepaper by bonding the fibers thereof together and retarding the rate ofdisintegration of the kraft sheet under outside storage conditions. As aresult, clearly the longer the paper sheet remains intact, the life ofthe polypropylene sheet is proportionately prolonged.

To further prolong the useful life expectancy of the bags, formed inaccordance with the present invention the outer ply of paper may betreated with conventional mold proofing agents which are known in theart.

The composite webs constructed in accordance with the present inventionare useful in other applications in addition to the production of sand,rip-rap bags, or the like. In particular, the material may be used toform wrappers or packages of various types, and it is contemplated thatthe material may be used to form cotton bale wraps. In'such cases, it isdesirable that the product which is to be wrapped in the web beprotected from contamination by the spunbonded polypropylene fibers. Insuch cases a layer of paper is laminated to the interior surface 32 ofthe polypropylene sheet in order to prevent such contamination. Thus,the paper sheet 30, as seen in FIG. 5, will provide the barrier toultraviolet radiation to prevent actinic degradation of thepolypropylene sheet while the inner layer 34 protects the product withinthe wrapper from contamination. Further, the provision of a paper ply onboth sides of the polypropylene sheet presents a smooth surface on thepackage and eliminates the roughness often associated with spunbondedpolypropylene sheeting.

In yet another embodiment of the present invention, (FIG. 6), awaterproofing inner liner 38 formed from a material such as polyethyleneis inserted in bag 10. The liner may typically be in the form of a flushcut tube inserted in the bag with its bottom edge sewn or taped closedwith the remainder of the bag, as illustrated at 40 in FIG. 1. Liners ofthis nature are preferably used to protect the contents of the bag fromdeterioration due to any moisture which might enter the bag through thepaper and polypropylene sheets 26 and 22.

In one contemplated use of this embodiment of the present invention,caustic soda may be contained within the bag 10. This material rapidlydeteriorates paper bags, and in previously proposed bags and inner linerwas supplied which has a top cuff portion overlying the top edge of thebag. The cuff prevented the caustic soda from entering the space betweenthe liner and side walls of the bag during loading. While suchprecaution increased the life of the bag, the provision of the cuffresulted in increased manufacturing costs and reduced packing rates.With the present embodiment of the invention, however, no cuff isrequired as the inner layer 22 of polypropylene is unaffected by thecaustic soda and so even if this material were inadvertently appliedbetween the liner and the sidewall of the bag, the paper ply 26 wouldnot be effected. As a result manufacturing time is decreased and thepacking rates are increased. The benefits of this embodiment of theinvention are clearly equally avoidable when packing other materialsthan caustic soda which must be kept dry and/or which tends todeteriorate paper.

In the preferred form of this embodiment, inner liner 38 is secured tothe bag only at a small number of locations by a conventional adhesiveor by spot heat welding. However, liner 38 may be secured along itsentire extent to polypropylene layer 22. Further, the top of inner liner38 may be closed by a simple heat sealing operation. In any case, thepolypropylene liner serves to provide increased strength and toughnessto the bag construction while the outer paper bag protects thepolypropylene from actinic degradation While the preferred embodimentsof the invention as described above are constructed primarily withspunbonded polypropylene materials it is contemplated that multiwall bagconstruction according to the present invention may also be formed withother materials which are subjected to actinic degradation. For example,satisfactory multiwall bags have been formed from spunbonded nylon andfilm or sheet polypropylene.

Although illustrative embodiments of the invention have been describedherein with reference to the accompanying drawings, it is to beunderstood that the invention is not limited to those preciseembodiments, and that various changes and modifications may be effectedtherein by one skilled in the art without departing from the scope orspirit of this invention.

What is claimed is:

1. A bag construction comprising an inner article supporting bag memberand an outer protective bag member laminated together by an adhesivematerial, said inner bag member being formed of non-woven porousspunbonded polypropylene which provides the article supporting strengthto the bag construction, and said outer bag member being formed of kraftpaper for protecting said spunbonded polypropylene article supportingbag against actinic degradation.

2. A bag construction as defined in claim 1 wherein said adhesivematerial is selected from the group consisting of latex solutionadhesive, asphalt, polymer wax, acetate and hot melt adhesive.

3. A bag construction as in claim 1 wherein said outer bag member isformed of a plurality of plies of paper.

4. A bag construction as in claim 3 wherein said paper plies arelaminated together.

5. A bag construction as defined in claim 1 including a paper bag membergenerally conforming in configuration to said inner bag member andpositioned within the latter whereby said inner bag member is locatedbetween said paper bag members.

6. A bag construction as defined in claim 1 including a second innerbarrier bag member generally conforming in configuration to saidspunbonded polypropylene inner article supporting bag member and beingformed of a water impervious material, said second inner bag memberbeing positioned within said spunbonded polypropylene bag member as awaterproof barrier preventing discharge of liquid through saidspunbonded polypropylene bag.

7. A bag construction as defined in claim 6 wherein said second innerbag member is formed of polyethylene.

8. A bag construction comprising an article supporting bag formed of aspunbonded olefinic polymer material providing the structural articlesupporting member of said bag construction, said spunbonded articlesupporting bag having an outer surface, and at least one ply ofprotective paper secured to said outer surface to protect saidspunbonded olefinic polymer bag against actinic degradation.

9. A bag construction as defined in claim 8 wherein said paper ply islaminated to said spun bonded olefinic polymer bag by an adhesivematerial.

10. A bag construction as defined in claim 9 wherein said spun bondedolefinic polymer material is spunbonded polypropylene.

11. A bag construction as defined in claim 10 wherein said bag has aninner surface and at least one ply of paper is secured to said innersurface.

12. A bag construction as defined in claim 10 including a plurality ofplies of paper secured to said outer surface.

13. A bag construction as defined in claim 12 wherein said paper pliesare laminated to said bag and to each other in superimposed relation byan adhesive material.

14. A bag construction as defined in claim 8 including an inner bagmember generally confirming in configuration to said olefinic polymerbag and being formed of a water impervious material, said inner bagmember being positioned within said olefinic polymer bag.

15. A bag construction as defined in claim 14 wherein said inner bagmember is formed of polyethylene.

1. A bag construction comprising an inner article supporting bag memberand an outer protective bag member laminated together by an adhesivematerial, said inner bag member being formed of nonwoven porousspunbonded polypropylene which provides the article supporting strengthto the bag construction, and said outer bag member being formed of kraftpaper for protecting said spunbonded polypropylene article supportingbag against actinic degradation.
 2. A bag construction as defined inclaim 1 wherein said adhesive material is selected from the groupconsisting of latex solution adhesive, asphalt, polymer wax, acetate andhot melt adhesive.
 3. A bag construction as in claim 1 wherein saidouter bag member is formed of a plurality of plies of paper.
 4. A bagconstruction as in claim 3 wherein said paper plies are laminatedtogether.
 5. A bag construction as defined in claim 1 including a paperbag member generally conforming in configuration to said inner bagmember and positioned within the latter whereby said inner bag member islocated between said paper bag members.
 6. A bag construction as definedin claim 1 including a second inner barrier bag member generallyconforming in configuration to said spunbonded polypropylene inneRarticle supporting bag member and being formed of a water imperviousmaterial, said second inner bag member being positioned within saidspunbonded polypropylene bag member as a waterproof barrier preventingdischarge of liquid through said spunbonded polypropylene bag.
 7. A bagconstruction as defined in claim 6 wherein said second inner bag memberis formed of polyethylene.
 8. A bag construction comprising an articlesupporting bag formed of a spunbonded olefinic polymer materialproviding the structural article supporting member of said bagconstruction, said spunbonded article supporting bag having an outersurface, and at least one ply of protective paper secured to said outersurface to protect said spunbonded olefinic polymer bag against actinicdegradation.
 9. A bag construction as defined in claim 8 wherein saidpaper ply is laminated to said spun bonded olefinic polymer bag by anadhesive material.
 10. A bag construction as defined in claim 9 whereinsaid spun bonded olefinic polymer material is spunbonded polypropylene.11. A bag construction as defined in claim 10 wherein said bag has aninner surface and at least one ply of paper is secured to said innersurface.
 12. A bag construction as defined in claim 10 including aplurality of plies of paper secured to said outer surface.
 13. A bagconstruction as defined in claim 12 wherein said paper plies arelaminated to said bag and to each other in superimposed relation by anadhesive material.
 14. A bag construction as defined in claim 8including an inner bag member generally confirming in configuration tosaid olefinic polymer bag and being formed of a water imperviousmaterial, said inner bag member being positioned within said olefinicpolymer bag.
 15. A bag construction as defined in claim 14 wherein saidinner bag member is formed of polyethylene.